Portable helmet

ABSTRACT

A portable helmet is disclosed that provides a level of protection at least comparable to conventional non-portable helmets, with the added function of being quickly portable for storage and transport. The helmet includes a series of interlocking curved wedges that can be rotated along pivot-points located on a center support. Wedges to the front of the center support rotate along a front pivot-point, while wedges to the rear of the center support rotate along a rear pivot-point. The curved wedges rotate to nest under the center support when in the closed position and form a wearable helmet when rotated into the extended position.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 61/087,542, filed Aug. 8, 2008, incorporated by reference herein in its entirety.

BACKGROUND

As construction techniques become ever-more efficient, travel among jobsites by workers from the field-level, as well as the engineering- and management-levels, has become increasing frequent. While most large contractors keep an onsite supply of cheap hard hats to give out to short-term visitors, these hard hats are not always available, leading many workers to enter jobsites without proper head protection.

Currently, the hard hat industry is largely divided between cheaper “throw away” hard hats that are quickly discarded and seldom moved from site to site, and more expensive “specialty hats” that have more aesthetically appealing designs. These specialty hats are typically well cared for by their owners, but they share the common trait of being bulky and difficult to transport. As such, the specialty hats are often left at a central location and not taken to infrequently-visited jobsites.

An aesthetically appealing, portable hard hat would solve the problem of easy transport, encourage specialty hat owners to carry their hats with them, and reduce the wasteful use of “throw away” hard hats.

SUMMARY

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In one aspect, a portable helmet is provided, the portable helmet comprising: a center support defining a forward pivot axis and a rearward pivot axis; a plurality of front curved wedges attached to the center support to pivot about the forward pivot axis such that the front curved wedges are pivotable between an extended position wherein the front curved wedges define a front portion of the helmet and a closed position wherein the front curved wedges nest under the central support; a plurality of rear curved wedges attached to the center support to pivot about the rearward pivot axis such that the rear curved wedges are pivotable between an extended position wherein the rear curved wedges define a rear portion of the helmet and a closed position wherein the rear curved wedges nest under the central support; and means for locking the front and rear curved wedges in the extended position.

In another aspect, a portable helmet is provided, the portable helmet comprising: a center support defining a forward pivot axis and a rearward pivot axis; a plurality of front curved wedges attached to the center support to pivot about the forward pivot axis such that the front curved wedges are pivotable between an extended position wherein the front curved wedges define a front portion of the helmet and a closed position wherein the front curved wedges nest under the central support; a plurality of rear curved wedges attached to the center support to pivot about the rearward pivot axis such that the rear curved wedges are pivotable between an extended position wherein the rear curved wedges define a rear portion of the helmet and a closed position wherein the rear curved wedges nest under the central support; and a clasp for locking the front and rear curved wedges in the extended position, formed between adjacent wedges.

In another aspect, a portable helmet is provided, the portable helmet comprising: a center support defining a forward pivot axis and a rearward pivot axis; a plurality of front curved wedges attached to the center support to pivot about the forward pivot axis such that the front curved wedges are pivotable between an extended position wherein the front curved wedges define a front portion of the helmet and a closed position wherein the front curved wedges nest under the central support; a plurality of rear curved wedges attached to the center support to pivot about the rearward pivot axis such that the rear curved wedges are pivotable between an extended position wherein the rear curved wedges define a rear portion of the helmet and a closed position wherein the rear curved wedges nest under the central support; and a fastener tab attached to the center support and fastener holes on each individual front and rear curved wedge to accommodate insertion of the fastener tab only when all wedges are fully extended or closed.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 shows a perspective side-view of a helmet in accordance with the present invention in its deployed form, ready to be worn;

FIG. 2 shows a fragmentary side-view of the helmet shown in FIG. 1, including a representative tab-based fastening system with the hat in its deployed form and the fasteners open;

FIG. 3 shows a perspective side-view of the tab-based fastening system of the helmet shown in FIG. 1, with the helmet in its closed form and tabs open;

FIG. 4 shows a fragmentary interior-view of the tab-based fastening system of the helmet shown in FIG. 1, with the fasteners closed;

FIG. 5 shows an inverted view of the helmet shown in FIG. 1, in its closed form;

FIG. 6 shows a perspective side-view of an embodiment of the helmet in accordance with the present invention that includes fully-exposed alignment ridges;

FIG. 7 shows a perspective side-view of the helmet in one embodiment which includes semi-recessed ridges, and includes a ventilation gap between wedges;

FIG. 8 shows an interior view of a representative fastening system that includes a Z clasp that locks adjacent wedges to one another;

FIG. 9 shows cross-sectional view of the Z clasp mechanism illustrated in FIG. 8;

FIG. 10 shows a side-view of the inner headgear, or lining;

FIG. 11 shows a perspective view of the inner headgear as seen from above;

FIG. 12 shows a side-view of the inner headgear with the helmet superimposed over it;

FIG. 13 shows a side-view of the inner headgear with arrows showing the direction of collapse, with the helmet superimposed over it;

FIG. 14 shows a side view of the inner headgear in its closed form, with the helmet superimposed over it; and

FIG. 15 shows the inner headgear installed into the helmet, as seen from above.

FIG. 16 is a side view of one embodiment of the provided helmet that does not have tabs as a fastening system but instead employs interlocking clasps or friction to immobilize the wedges in the fully-deployed position;

FIG. 17 is an underside view of the helmet of FIG. 17;

FIG. 18 is a transparent side view of a helmet similar to that illustrated in FIG. 17 when in a fully-stowed position;

FIG. 19 is a detail perspective view of an interlocking clasp, prior to clasping, useful in the embodiments described herein;

FIG. 20 is a detail perspective view of the interlocking clasp shown in FIG. 19, yet advanced further towards clasping; and

FIG. 21 is a detail perspective view of the interlocking clasp shown in FIGS. 19 and 20, advanced to a clasped position.

DETAILED DESCRIPTION

In one aspect, a portable helmet is provided, the portable helmet comprising: a center support defining a forward pivot axis and a rearward pivot axis; a plurality of front curved wedges attached to the center support to pivot about the forward pivot axis such that the front curved wedges are pivotable between an extended position wherein the front curved wedges define a front portion of the helmet and a closed position wherein the front curved wedges nest under the central support; a plurality of rear curved wedges attached to the center support to pivot about the rearward pivot axis such that the rear curved wedges are pivotable between an extended position wherein the rear curved wedges define a rear portion of the helmet and a closed position wherein the rear curved wedges nest under the central support; and means for locking the front and rear curved wedges in the extended position.

The present invention is a helmet (also referred to herein as a “hard hat”), comprising a series of curved wedges, as shown in the multiple views of an embodiment illustrated in FIGS. 1-6. The wedges extend laterally across the width of the helmet and attach at a pair of oppositely-disposed pivot points on the central support 102 (FIG. 4 illustrates two pivot points 132 and 134, as will be described below). The wedges rotationally stow under, or extend and deploy from beneath, the center support 102 (also referred to herein as a “central wedge”).

The wedges rotate about pivot points (e.g., 120 and 126) that come in pairs (the paired pivot points to 132 and 134 are not illustrated) that are typically transversely located on the latitudinal sides of the center support 102. In the embodiment illustrated in FIG. 1, two pairs of pivot points are illustrated: wedges 104, 106, 108, and 110 pivot around a front pivot point 132 and wedges 112, 114, and 116 pivot around a rear pivot point 134 (e.g., FIG. 3). The wedges can expand to form a protective helmet (e.g., FIG. 1), or collapse into a folded configuration. FIG. 1 shows the helmet in its fully expanded (“deployed”) form, ready to wear by a user. The center support 102 provides the housing into which all of the other wedges can collapse and nest.

As each wedge locks during expansion, or mates, with the wedge(s) next to it, the wedge immediately tangential to a given wedge is considered its “mating wedge.” As described herein, wedges 104, 106, 108, and 110 comprise the front wedges, while wedges 112, 114, and 116 comprise the rear wedges. As the center support 102 is located in the center of the helmet 100, all front and rear wedges are progressively lower in profile than the center support 102, creating downward connections and preventing liquid from above from leaking into the helmet.

The front wedges 104, 106, 108, and 110 rotate about a forward pivot axis created by the pair of pivot points (e.g., 132 and its paired, oppositely-disposed pivot point). Similarly, the rear wedges 112, 114, and 116 rotate about a rear pivot axis created by a pair of pivot points (e.g., rear pivot point 134 and its paired, oppositely-disposed pivot point).

The front pivot point is shown as 132 and the rear pivot point is shown as 134. FIG. 4 has been illustrated to make these pivot points highly visible for illustrative purposes. In one embodiment of the invention, the lynchpins (not illustrated) upon which the wedges rotate at said pivot points are ultrasonically welded in place, making them nearly invisible.

Means for locking the front and rear curved wedges are provided. Such means are also referred to as a “fastening system” herein. Representative locking means include friction between wedges, a fastener tab system, a clasp system between wedges, and combinations thereof.

A representative fastening system is the fastener tab system 118 that includes fastener tabs 122 and 124, housed in a molded housing, that are sized and configured to insert into holes 120 and 126 that pass through openings in each wedge when the wedges are fully stowed or fully deployed so as to secure the helmet 100 in the desired position. Parts 120 and 122 comprise a front fastening system, while 124 and 126 comprise a rear fastening system. In one embodiment the space between the front tab 122, and the rear tab 124, in the housing 118 contains an insert tab for accepting a visor or face protection accessory (not illustrated).

To prevent any possibility of improper use, the tab fastening system 118, is designed so that locking the fasteners is only achievable when all of the wedges are in their properly expanded (or, optionally, contracted) form. FIG. 2 shows the helmet in its expanded form, ready to be locked. Accordingly, 120 and 126 show fastener-holes that properly align to allow the fastening tabs, 122 and 124, to push into place. Conversely, FIG. 3 shows the helmet in its closed form, where the fastener-holes 120 and 126 do not align, preventing insertion of the fastener tabs 122 and 124. In one embodiment, each fastener-hole (e.g., 120) is progressively sized, with the center support 102, containing the largest fastener-hole. In this embodiment, wedges 110 and 112 have fastener-holes of equal size, slightly smaller than the fastener-hole in the center support 102. Wedges 108 and 114 again have faster-holes of equal size, slightly smaller than the fastener holes in 110 and 112. This continues progressively so that 104 and 116 have the smallest fastener-holes, again of equal size. Accordingly, the fasteners 122 and 124 are tapered so that when inserted into the properly aligned fastener-holes the tapered stalk of the fastener fits snugly against each hole in each progressive wedge. In this embodiment, both 122 and 124, the tapered fastener-tabs, have a split-squeeze design with an ellipse-head at the end. The head is squeezed together during insertion, temporarily making a transverse dimension of the head smaller and allowing the tab to slide into place through all of the wedges. After passing through the final front wedge and back wedge, 104 and 116, respectively, the tabs are free to expand, locking themselves into place, as shown in FIG. 4. The tabs can therefore only be released by removing the helmet from the head and squeezing while simultaneously pushing the tabs outward from the interior. The considerable gap between the outer shell and the inner headgear prevents any chance of accidentally bumping the fasteners during use.

As shown in FIG. 1 the tab fastening system 118, allows the fasteners 122 and 124 to insert into the holes and fit flush against the side of the helmet 100 when fully expanded, avoiding any chance for protrusions to snag on debris, disproportionately absorb impact, or otherwise compromise the structural integrity or safety of the helmet.

In closed form (e.g., FIG. 3), the wedges abut against each other and are immobilized by a fastening system. Representative fastening systems, as previously mentioned, include friction between the wedges, the above-described tab mechanism 118, or a tab stop 420, illustrated in FIG. 18.

In one embodiment, the fastening system is a Z clasp 170 locking mechanism, as shown in FIGS. 8 and 9. Z clasps are known to those of skill in the art and will not be described in further detail.

In one embodiment, the locking system is an interlocking clasp 510, as illustrated in FIGS. 19-21. The interlocking clasp 510 includes an upper clasp portion comprising an upper tab 512 and an upper notch 516 formed on an upper ridge 518 of an upper wedge 502 of a helmet 500. The interlocking clasp 510 also includes a lower clasp portion comprising a lower tab 514 and a lower ridge 520. The interlocking clasp 510 is shown in a closed position in FIG. 21 such that the lower wedge 504 is prevented from extending further because the lower tab 514 will be impeded by the upper tab 512. Additionally, when clasped, the lower wedge 504 is prevented from collapsing into the upper wedge 502 because the lower ridge 520, disposed within the upper notch 516 will be impeded by the upper ridge 518. The illustrated interlocking clasp 510 is released with upward pressure on the upper wedge 502 such that the upper wedge 502 and lower wedge 504 are sufficiently separated such that the interlocking clasp 510 is disabled.

FIG. 5 shows an inverted interior view of an embodiment of the helmet in its closed form.

In one embodiment, the wedges are formed with overhead interlocking ridgelines 142 to mitigate lateral torque and add overall structural stability, as shown in FIG. 6. The ridge design instills additional structural strength in the event of an overhead or side impact, and also aids in aligning the wedges during collapsing and expanding of the helmet 100.

In one embodiment the ridges are fully exposed, as shown in FIG. 6. In another embodiment the ridges 162 are semi-recessed, as shown in FIG. 7. Recessing the ridges 162 in this embodiment is possible because the rotational access of each individual wedge is tighter then the curve of the overall fully-expanded helmet 100. Thus, each wedge begins to pull away from its mating wedge(s) during collapse towards the stowed position. The recess angle for the ridges follows the curve of each individual wedge as it pivots towards the closed form.

The helmet 100 of FIG. 7 includes a ventilation gap 164.

In one embodiment, the center support can be split such that the helmet includes a first center support, and a second center support, each with at least one pair of pivot points.

In one embodiment, the helmet further comprises a portable inner headgear 200 attached to the helmet 100, the inner headgear 200 being sized and configured to directly engage a user's head. The inner headgear 200, or lining, is designed to collapse and expand along with the outer shell. Attaching and detaching the inner headgear 200 on traditional hard hats is time-consuming, and it can be reasonably assumed that extra setup time to affix the lining would prove inconvenient enough to discourage users from collapsing and expanding after each use, thus functionally negating the primary utility of a portable hard hat. FIG. 10 shows a side view of the inner headgear 200 in its expanded form. Pivot points 185 and 187 on the inner headgear align with the pivot points 132 and 134 in the outer shell of the helmet. During use, the rear portion of the inner headgear 184 and 186, will protrude slightly beyond the outer shell to aid stability and effectively keep the helmet 100 on the user's head. Part 184 is the ratcheting section, while 188 is the ratcheting handle. Turning the handle 188 clockwise will pull the rear section 186 to tighten, while turning the handle 188 counter-clockwise will cause it to loosen. Users may adjust the hat in this way to fit the exact size of their heads. Unlike traditional hard hat inner headgear, the angle of the rear portion 186 and 188, can be adjusted by the user for comfort. Additionally, the rear portion 184 and 188, can be pivoted 180 degrees inward during collapse to avoid protrusion.

The front section of the inner headgear 200 is shown as 180, the middle section as 182, and the upper-rear is shown as 184. These pieces have mirror duplicates on the opposite side of the inner headgear. Each of these pieces will attach individually to the inside wall of the outer shall through insert tabs.

A fully inserted inner headgear system with the outer shell of the helmet superimposed on top is shown in FIG. 12. FIG. 13 further illustrates the collapse motion through arrows and shading. Lightly shaded pieces are in the closed position, while arrows show the pivot direction, starting from the expanded position. FIG. 14 shows the inner headgear in the fully closed position with the helmet superimposed on the top. The ratchet handle 188 is protruding.

A flexible strap system 189 is attached to insert tabs (one of which is shown as 202) so that the straps bisect the helmet and intersect at the crown. In one embodiment this flexible strap system is VERSAFLEX®, or a similar rubber-based substance, which is a substitute for traditional nylon straps that does not tend to retain odor, does not tend to discolor from sweat, and is gentler to the touch. In another embodiment this strap system is nylon.

FIG. 11 shows the complete inner headgear 200, as seen from above. Insert tabs, such as 202, are placed at the endpoints of the flexible strap system 189. In FIG. 10, part 183 is a location for attaching the flexible strap system 189 to the inner headgear 200. The corresponding insertion slot is part of the molded design of the inside wall of the outer shell in each wedge that accepts inner headgear insertion tabs.

FIG. 15 shows the inner headgear inserted into the helmet, as seen from below. Insert slots are molded into the inner side of the outer shell at the endpoint of each strap in the flexible strap system, and insert tabs are attached to each end of the corresponding strap to fit into the insert slots.

When in the closed position (e.g., FIGS. 3 and 18), the helmet is at its most compact, and the dimensions of the helmet substantially match those of the center support (e.g., 102). The compact dimensions facilitate the portability of the helmet.

FIGS. 16-18 illustrate various views of an embodiment of the invention that does not use a tab-based fastening system, but instead relies on friction between the wedges or an interlocking clasp system for immobilization of the helmet in a closed or expanded position. Referring to FIG. 16, a side view of a helmet 300 is illustrated in an expanded position. The helmet 300 includes a center support 302, front wedges 311 (individually, 304, 306, 308, and 310), and rear wedges 317 (individually, 312, 314, and 316). Referring to FIG. 17, a bottom view of the helmet 300 is illustrated, with the bottom side of the front and rear wedges shown. Additionally, ridges 330 on the underside of the wedges and center support 302 are illustrated. As described previously, ridges can be included to provide torsional, longitudinal, and lateral stability to the helmet 300. Additionally, illustrated in FIG. 17 are the attachment points between the wedges and the center support 302. The attachment assembly 320 includes, in this illustrated representative embodiment, a pin 322 passing through (at a pivot point) the three wedges 312, 314, 316 (the combination of the three at the pivot point being labeled as part 324).

FIGS. 16 and 17 additionally illustrate the interface between the center support 302 and front wedge 310 at an interface location marked 318. At the interface between the center support 302 and a wedge (e.g., 310) or between wedges (e.g., 310 and 308), a means for locking the mating pieces together is provided. Representative examples of this locking means include friction, or an interlocking clasp system, as described above. In the embodiment illustrated in FIGS. 16-18, friction is used as the locking means, as no interlocking clasp system is illustrated.

Referring to FIG. 18, the helmet 400 is illustrated in closed form (e.g., the helmet 300 of FIGS. 16 and 17 closed) such that the center wedge 402 has nested within it the front and rear wedges 404, 406, 408, 410, 412, 414, and 416. The width of the center wedge 402 is approximately equal to the width of the entire helmet 400 in the closed position. Additionally illustrated in FIG. 18 is a lock tab 420 that provides a rotational stopping point for the front and rear wedges. In the embodiment illustrated in FIG. 18, the front wedges 406, 408, and 410 rotate on front pivot point 425 and each wedge includes a notch 422 (numbered collectively for all wedges) and the rear wedges rotate on a rear pivot point 425 and include a rear notch 424 (collectively labeled for wedges 312, 314, and 316). When the wedges rotate toward the closed position, the notches 422 and 424 on the wedges prevent the wedges from traveling further toward the closed position when they abut the locking tab 420. The locking tab 420 may additionally provide friction at the notches 422 and 424 that prevents the wedges from opening unless force is applied by the user. In one embodiment, the interface between the locking tab 420 and the notches 422 and 424 is a Z clasp.

In one embodiment, the front and rear curved wedges are sufficiently hard to protect a wearer from above impacts.

In one embodiment, the front and rear curved wedges are not electrically conductive.

In one embodiment, the front and rear curved wedges are sufficiently hard to protect a wearer from above impacts.

In one embodiment, wherein the front and rear curved wedges are not electrically conductive.

In one embodiment, the front and rear curved wedges are plastic.

In one embodiment, the helmet is made primarily out of ABS plastic (acrylonitrile butadiene styrene) which is hard enough to resist side or overhead impact. For head-protection purposes, the most important mechanical properties of ABS are resistance and toughness. A variety of modifications can be made to improve impact resistance, toughness, and heat resistance. The impact resistance can be amplified by increasing the proportions of polybutadiene in relation to styrene and acrylonitrile. Impact resistance does not fall off rapidly at lower temperatures, making it ideal for the hard hat application. Stability under load is excellent with limited loads. ABS is not an electrical conduit.

In one embodiment, the plastic comprises a polycarbonate. Polycarbonate plastic is derived from bisphenol A. Polycarbonate is a very durable material, and can be laminated to make bullet-resistant glass or other material. Polycarbonate plastic is electrically non-conductive.

In one embodiment, the front and rear curved wedges are fiberglass. Fiberglass is comprised of glass fibers which are useful because of their high ratio of surface area to weight. Fiberglass is electrically non-conductive.

In another aspect, a portable helmet is provided having a clasp locking system, the portable helmet comprising: a center support defining a forward pivot axis and a rearward pivot axis; a plurality of front curved wedges attached to the center support to pivot about the forward pivot axis such that the front curved wedges are pivotable between an extended position wherein the front curved wedges define a front portion of the helmet and a closed position wherein the front curved wedges nest under the central support; a plurality of rear curved wedges attached to the center support to pivot about the rearward pivot axis such that the rear curved wedges are pivotable between an extended position wherein the rear curved wedges define a rear portion of the helmet and a closed position wherein the rear curved wedges nest under the central support; and a clasp for locking the front and rear curved wedges in the extended position, formed between adjacent wedges.

In another aspect, a portable helmet is provided having a tab-based locking system, the portable helmet comprising: a center support defining a forward pivot axis and a rearward pivot axis; a plurality of front curved wedges attached to the center support to pivot about the forward pivot axis such that the front curved wedges are pivotable between an extended position wherein the front curved wedges define a front portion of the helmet and a closed position wherein the front curved wedges nest under the central support; a plurality of rear curved wedges attached to the center support to pivot about the rearward pivot axis such that the rear curved wedges are pivotable between an extended position wherein the rear curved wedges define a rear portion of the helmet and a closed position wherein the rear curved wedges nest under the central support; and a fastener tab attached to the center support and fastener holes on each individual front and rear curved wedge to accommodate insertion of the fastener tab only when all wedges are fully extended or closed.

While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention. 

1. A portable helmet, comprising: (a) a center support defining a forward pivot axis and a rearward pivot axis; (b) a plurality of front curved wedges attached to the center support to pivot about the forward pivot axis such that the front curved wedges are pivotable between an extended position wherein the front curved wedges define a front portion of the helmet and a closed position wherein the front curved wedges nest under the central support; (c) a plurality of rear curved wedges attached to the center support to pivot about the rearward pivot axis such that the rear curved wedges are pivotable between an extended position wherein the rear curved wedges define a rear portion of the helmet and a closed position wherein the rear curved wedges nest under the central support; and (d) means for locking the front and rear curved wedges in the extended position.
 2. The portable helmet of claim 1, wherein each of the plurality of front curved wedges includes a ridge, and wherein the ridges are aligned to engage the ridges on adjacent front curved wedges.
 3. The portable helmet of claim 1, where the front and rear curved wedges are sufficiently hard to protect a wearer from above impacts.
 4. The portable helmet of claim 1, wherein the front and rear curved wedges are not electrically conductive.
 5. The portable helmet of claim 1, wherein the front and rear curved wedges are plastic.
 6. The portable helmet of claim 5, wherein the plastic comprises a polycarbonate.
 7. The portable helmet of claim 1, wherein the front and rear curved wedges are fiberglass.
 8. The portable helmet of claim 1, wherein the center support defines the front pivot axis with a first pair of oppositely disposed pivots and defines the rear pivot axis with a second pair of oppositely disposed pivots, wherein the front curved wedges are attached to the center support at the first pair of pivots and the rear curved wedges are attached to the center support at the second pair of pivots.
 9. The portable helmet of claim 1, wherein the center support comprises a first center support and a second center support, each with at least one pair of pivot points.
 10. The portable helmet of claim 1 further comprising a portable inner headgear attached to the helmet, the inner headgear being sized and configured to directly engage a user's head.
 11. The portable helmet of claim 10, wherein the inner headgear comprises means for locking the front and rear curved wedges in the closed position.
 12. The portable helmet of claim 1, wherein the means for locking the front and rear curved wedges in the extended position is friction between adjacent front and rear curved wedges.
 13. The portable helmet of claim 1, wherein the means for locking the front and rear curved wedges in the extended position is a clasp formed between adjacent wedges.
 14. The portable helmet of claim 1, wherein the means for locking the front and rear curved wedges in the extended position is a fastener tab attached to the center support and fastener holes on each individual front and rear curved wedge to accommodate insertion of the fastener tab only when all wedges are fully extended or fully closed.
 15. The portable helmet of claim 1, wherein when the front and rear curved wedges are all in the closed position the helmet has a smallest dimension that is equal to the smallest dimension of the central support.
 16. A portable helmet, comprising: (a) a center support defining a forward pivot axis and a rearward pivot axis; (b) a plurality of front curved wedges attached to the center support to pivot about the forward pivot axis such that the front curved wedges are pivotable between an extended position wherein the front curved wedges define a front portion of the helmet and a closed position wherein the front curved wedges nest under the central support; (c) a plurality of rear curved wedges attached to the center support to pivot about the rearward pivot axis such that the rear curved wedges are pivotable between an extended position wherein the rear curved wedges define a rear portion of the helmet and a closed position wherein the rear curved wedges nest under the central support; and (d) a clasp for locking the front and rear curved wedges in the extended position, formed between adjacent wedges.
 17. The portable helmet of claim 16, wherein the clasp is a clasp selected from the group consisting of a Z clasp, an interlocking clasp, and an interlocking Z clasp.
 18. A portable helmet, comprising: (a) a center support defining a forward pivot axis and a rearward pivot axis; (b) a plurality of front curved wedges attached to the center support to pivot about the forward pivot axis such that the front curved wedges are pivotable between an extended position wherein the front curved wedges define a front portion of the helmet and a closed position wherein the front curved wedges nest under the central support; (c) a plurality of rear curved wedges attached to the center support to pivot about the rearward pivot axis such that the rear curved wedges are pivotable between an extended position wherein the rear curved wedges define a rear portion of the helmet and a closed position wherein the rear curved wedges nest under the central support; and (d) a fastener tab attached to the center support and fastener holes on each individual front and rear curved wedge to accommodate insertion of the fastener tab only when all wedges are fully extended or closed.
 19. The helmet as in claim 18 wherein the fastener tabs are tapered to fit progressively smaller fastener-holes in the curved wedges. 